Electrostatic Field Effects in Covalent Organic Frameworks for Photocatalytic CO ₂ ‐to‐CO Conversion beyond 1000 mmol g _Co ⁻¹ h ⁻¹

Abstract

ABSTRACT Covalent Organic Frameworks (COFs) with unique π‐structures and exceptional stability are promising candidates for photocatalytic CO 2 conversion. However, most reported COFs exhibit significant recombination of photo‐generated charges and holes, along with low CO 2 chemisorption, leading to suboptimal photocatalytic performance. Here, we designed covalently linked two‐dimensional cobalt (II) porphyrin layers and introduced various tetra‐alkylammonium cations (─CH 2 N + (CH 3 ) 3 , ─CH 2 CH 2 N + (CH 3 ) 3 , or ─CH 2 CH 2 CH 2 N + (CH 3 ) 3 ). The tetra‐alkylammonium cations within the ionic covalent organic framework (iCOF) stabilize the intermediates of the photoreduction reaction and accelerate the reaction kinetics through electrostatic field interactions, thereby facilitating the conversion of *CO 2 to *CO. Molecular dynamics simulations further indicate that tetra‐alkylammonium side chains increase CO 2 residence time in the pores, thereby enhancing interaction with catalytically active sites. Furthermore, the electrostatic field effects of the tetra‐alkylammonium cations increase the charge density at the Co center, stabilize CO 2 reaction intermediates, and facilitate proton transfer. Remarkably, these advantageous effects synergistically contribute to the photocatalytic CO 2 ‐to‐CO conversion. The CoTph‐3C‐N + COF achieves an impressive CO initial production rate of 1006 mmol g Co −1 h −1 and a quantum efficiency of 5.67% at 420 nm, which is 17 times that of the pristine COF. This strategy offers a novel approach to designing various photocatalytic systems aimed at efficient chemical transformations.